Rock drill bit



Aug 5, 1952 M. H. HUBBACK 2,606,004

Rocx DRILL BIT Filed July 15., 194e 2 srmETs-sx-xEET 1 IN V EN TOR.

ug- 5, 1952 x M. H. HuBBAcK 2,606,004

ROCK DRILL BIT Filed July l5, 1946 2 SHEETS-SHEET 2 INVENTOR. 5 M H- HuAc/c 6 0 MMX l Patented Aug. 5, 1952 UNITED STTES noon muni. Brr

Malcolm H. Hubback, Seattle, Wash., assignor, by mesne assignments, to Clarice E. Hubback Application July 15, 1946, Serial No. 683,639

2 Claims.

This invention relates to the art of detachable rock drill bits, and namely drill bits comprised of a comparatively short cylindrical section of metal formed upon one end with a cutting edge or edges and upon the other end presenting an internally threaded sleeve which allows the bity to be screwed upon the lower end of the drill rod.

Detachable rock drill bits, as originally known, were products of the forging art, but these forged bits did not permit reconditioning upon becoming dull, and the consequence has been that the forged bit has in recent years been largely displaced by a machined bit, the principal advantage professed for the latter being an ability to resharpen the bits as the cutting edges wear down. However, each said resharpening operation removes an appreciable part of the bits metal body, and the bits can therefore be resharpened only a limited number of times be :tore becoming useless.

It is my object to devise a detachable rock drill bit peculiarized in that the same may be produced as a forged product, and which may be thereafter forge-reconditioned.

The drill bit of the present invention, and the structure employed in reconditioning the same, are shown in the accompanying drawings, wherein:

Figure 1 is a view in elevation taken on broken line I l of Fig. 2 to illustrate a detachable rock drill bit produced in accordance with the present invention and here shown in the course of being reconditioned. The drill bit is broken away and shown partly in section.

Fig. 2 is a View partly in elevation and partly in longitudinal section, with the section taken on line 2 2 of Fig. 1.

Fig. 3 is a transverse section on line 3 3 of Fig. 2.

Fig. 4 is a perspective View of the improved drill bit.

Fig. 5 is a view of the drill bit taken partly in elevation and partly in section on line 5 5 of Fig. 6.

Fig. 6 is a front elevational View of the drill bit, and

Fig. '7 is a rear elevational View of the drill blt.

The nished bit of the present invention is illustrated in Figs. Il through 7 inclusive, and is a product of the forging art comprising a cutting head denoted by the numeral lil and a stockengaging internally thread sleeve l l. The sleeve is characterized in that the internal threads are interrupted at two or more points within the cir- (Cl. Z55-64) course of originally forging the bit from a steel cumference. The interruption occurs, by preference, at diametrically opposite sides, and there are accordingly provided two threaded sectors denoted l2 'and i3. The object in interrupting the threads is to admit of the employment of Van expansion-type thread-forming tool, both in the billet and when later reconditioning the bitby forging. In addition toA its said interrupted thread, the sleeve is further characterized in that the depth of the threaded socket formed therein exactly corresponds with a reduced threaded stud formed upon the outer end of the drill rod to which the bit is to be applied. Thus, when the bit is screwed onto the'stud end of the drill rod, there is developed not only a firm bearing engagement as between the exposed face of the sleeve and the shoulder which lies at the base of the threaded stud, but also a bottoming action of the tip of the drill rod and the floor of the socket. Now, to enlarge upon the purpose underlying the interruption of the threads, it is quite evident that a forged detachable bit which relies for its detachability upon threads cut into a mounting sleeve must, in order that such threads be formed in the forging operation, be produced by the use of a core. If this core is made solid, the contraction of the metal upon the core in consequence of changing temperature and the metalcompressing action of the core in course of forming practically preclude removal of the sleeve by reason of the latter reezing onto the core. In overcoming the problem, I reasoned that an interrupted thread works equally as efficiently as a continuous thread in so far as producing a separable connection is concerned, and an interrupted thread has this advantage, it permits the utilization of a retractible thread-forming tool, and given an ability to contract the tool for removal purposes, the difliculty previously experienced in withdrawing the thread-forming core from a forged bit would beV overcome.

The head of the sleeve Il is shown provided with two sets of diametrically opposed wings 39 which project laterally beyond the perimeter of the sleeve. The head end of each wing presents a pair of dii/erging cutting faces 4l which slope rearwardly from a radialV cutting edge I6 the outer end of which denes the outermost tip 40 of the wing. The outer edges 4l of each pair o1' cutting faces slope inwardly toward the longitudinal axis of the drill as they diverge from the wing tip, which is to say, the plane defined by each pair of said outer edges forms an acute angle with the respective cutting edge I6. The

each ,pair .of cutting `faces. Vsharpened the outer fedge of :the cutting face .,ismoved yrearwardly .to aposition substantially parallel to its original position lsuch vbeing permitted because the `scouring edge I extends rearouter wing surface is comprised of a pair of salient faces II and I8 having their line of juncture 45, which I designate as a scouring edge, commencing at the wing tip 40. These faces slope slightly inwardly and are preferably planar as shown.

When the faces I1 and I8 are planar they are trapezoidal with the shorter parallel edge 42 forming :part oftheztop :edges of the quadrilateral side wall 43 of the wing. At the rearmost edges 44 of these faces the pitch of the slope of the outer wing surface is increased so that the said surface mergeswith the sleeve before reaching the tail end thereof. The pitch of this steeper slope is not important whereas'rth'e-angular 'frelationship between the plane of-eachlpairsofouter edges 4I, and each scouring edgee45, withrespect to the cutting edges I 6 is vital to the longer cutting life which I achieve. Prior to my invention the scouring edge wouldhave sloped inwardly towand-,the longitudinalfaxis'of the bit an amount isumcient to intersect imaginary circles .normal -.-to `and centered -along -the .longitudinal axis vof .the f bit and passing through the outer edges 1of :the cutting faces.

-4 I so that my scouring .edges-'lie laterallybeyond '-.the-said imaginary circles. V:In other wordsgmy scouringedges 4.are the itotal locus of all points on ithe -outer surface f'of the wings between the respective Vpairs of outer .edges -most laterally 'removed fromthe vlongitudinal axis of the drill.

,Ipreferfto effectsuch results-by increasing the .acute-.angle .between lthe Ascouringedge and the Jespecti-ve ,cutting redige, -whieh said .increase strengthens the outer -tips of-,the wings. viButeyen tmore .important -is the fact ,that-'the cutting-.edges ,fI 6 .can be :re-sharpened .and :re-conditioned -zby .fasreforging operation, -to Ibe later described, in- `i -stead lof -by-a machining operationzas has 'been conventional, .and such reconditioning by re- .forging lcan be performed-avrgreater number of .tlmesthan vhas been-heretoforepossible, without .materially increasing ythe dihedral angler between When my bit is -.artfdrills the respective side walls are triangular in shape instead of-trapezoidal and the-rea-rmost rends of the outer .edges of their cutting-'faces eachstay in a virtually-constant; position f as'the .drill issharpened, thus accounting for'the fact .that the Vdihedral angle between'the cutting faces necessarily increases -as the drill is sharpened which reduces the euttingefliciency thereof.

The lhead I0 has a center bore:48 ,therethrough :connected tothe socket I4 in' the-sleeve. Between the wings the diameter of'the bit visthe same as '1thediameter ofthe sleevev to thereby form-.channels betweenthe sidewalls of the wings through which .dust .and fragments resulting from the cuttingv operation -.can be ejected by .the compressedair or water delivered .to .the cutting -faces through the bore 48.

Theprocess` of .forging-my .bit can 'be explained as follows:

A die body -isvemployed -which is composed of ,Aa-stationary member and a movable member ar- ;I have vincreased the angle s tbetween `the scouring edgeandthe plane common 'to-.the respective pair-.of.intersectingzouter edges -while producing the interrupted threads.

vmatic hammer.

ranged to be clamped thereto, and formed by these members in their mating faces are recesses producing, by registration, a cavity corresponding to the surface contour of the bit which is to be produced. An axially placed bore of small diameter connects from one end of the assembled die with the head end of the cavity, and a bore having a diameter coinciding with that of the back 4.end of the cavity leads to the cavity from the other end of the assembled die. The hot billet or slug which is to be forged is fed kthrough the large bore into this cavity, and an upsetting ram is driven hard against the billet from the back end of the latter. The upsetting `ram has. 9,;piston-head and a shoulder lying to the rear of'v the head, and the head, in point of its fshape, .roughly approximates the threaded socket which is to be produced in the sleeve of Athe finished bit. This shape, more especially, is

such as presents cut-away portions at diametri- .cally opposite -sides and with these reentrant openings, as with the diametrically opposed horns -whichlie therebetween, having their periineters made arcuateand concentric with the axis of the piston-head. It will be-understood that the `walls of this -piston-head Yare plane-faced, the

forming of the interrupted threads being the ofhce of a thread-forming tool employed in a llater step of the forging operation. The pistonhead -and its following -shoulder act'together to rsqueeze the billet into the crevices of the cavity,

and Work in conjunctionwith a piercing punch which is driven inwardly through the-small bore, and there'is produced-from this initial ramming step of my forging operation a 'forged product substantially similar to that illustrated in Figs.

f4 through .'7 of the drawings excepting that the lands which lie atdiametrically opposite sides of the bits rear-end socket are as yet lacking the threads of the finished'product. The next vstep is to transfer the-partially finished bit to -a -second clamping die having acavity corre- -sponding inpoint of its'side wall structure to the shape of the bit, and within Ithis latter die holding the forged bit against Va backing block Used for this vpurpose is a tool lhaving retractible thread-forming jaws, and this tool is quite similar in point of construction to the thread-reconditioning tool illustratedinFgs. l and 2, hence .need not'beseparately illustrated. There isnow produced a detachable rock drill bit in forged form having :the shape of the bit illustrated in the drawings.

For'forge-reconditioning my bit, there is employed a 'structure composed, as with the original forging dies, of a top and abottom die member, .and these die membersact in conjunction to produce a receiving cavity for the bit quite similar'to the-receiving cavity of the second of the two forming dies heretofore described. This is rto say that the die cavity substantially correspondsin point of its side wall structure to the external wall of the bit, and has its longitudinal wall-grooves, and namely those grooves into which the V-edges of the wings nt, prolonged forwardly a material distance beyond the die cavity proper. These prolongations of the wall grooves form a mounting to accommodate the slide movement of an upsetting and forming dolly which is arranged and adapted to be driven .against a bit occupying the cavity, the driving means being comprised, preferably, of a pneu- At the-other end of the cavity, .the die Ymembers accommodate the application of a thread-reconditioning tool held against end movement. Considering the similarity between the equipment which I use for forging my detachable rock drill bit and the equipment which I employ for reconditioning the bit, it is believed that an illustration of one set of such equipment, whether it be for forging or for forgereconditioning, should suffice for both. I have elected to illustrate my forge-reconditioning equipment, and referring to Figs. 1, 2 and 3, the top and bottom clamping dies are indicated by the numerals 20 and 2i, respectively. Denoted 22 is the forming dolly having a shank 23 arranged to nt a pneumatic hammer (not shown). rhe thread-reconditioning tool is made sectional and is comprised of a pair of arms 2:1-25 having opposingly mounted jaw or nose extremities 251-21, and formed upon the perimeter of these jaws are correlated threads produced as male counterparts of the interrupted left-hand internal threads of the drill bit. To the rear of the threads, each jaw or nose is formed with a respective semi-circular thrust collar 28 arranged to lodge in a mating recess of the die.

The arms are each hinged as at 29 to a body part 30, and there is received between the arms an expander pin 3|. Functional to this pin is a manually operated lever 32 forked upon its front end to straddle the pin, and providing a cam action as between the furcate branches 33 and a shoulder formed upon the pin. A split ring 3ft fits over the arms and performs a spring oce to yieldingly resist the expansive force of the expander pin. Other than for the employment of a power hammer to drive the expander pin, there is little difference between the expandable thread-reconditioning tool which I have illustrated and the expandable thread-forming tool used in the original forging of the bit, and which is to say the tool originally applied to produce the threads after having first created, by the use of an upsetting ram, a socket having lands therein at diametrically opposite sides.

It is believed that the invention will be clear from the foregoing. The heat employed in bringing to forging temperature the billet or the bit, as the case may be and according as the method concerned is an original forging operation or a forge-reconditioning procedure, is or may follow standard forging practice.

Having illustrated and described my invention and having explained the principles thereof, `it will be understood, nevertheless, that within the scope of the appended claims, the invention may be practised y otherwise than specifically illustrated and described. Furthermore, the phraseology or terminology employed herein is for purposes of description and not of limitation; for it is not intended to limit the invention beyond the requirements of the prior art.

What I claim is:

l. A drill bit comprising a shank having spaced wings projecting laterally therefrom, each wing being provided at its head end with a respective pair of rearwardly sloping cutting faces which merge to form a radial cutting edge whose outer end is the outermost tip of the respective wing,

the outer surface of each wing presenting a pair `of salient merging faces of trapezoidal outline each having the line of juncture between said salient faces as one of its parallel edges and the edge of the adjacent cutting face as another edge thereof with the latter said edge lying radially inward of the said line of juncture, the line of juncture of each wing dening ascouring edge commencing at the respective wing tip and extending rearwardly and sloping inwardly toward the longitudinal axis of the bit to a point of termination rearward of the outside edges of the respective pair of cutting faces and forward of the tail end of the wing.

2. A drill bit comprising a shank having spaced wings projecting laterally therefrom, each wing being provided at its head end with a respective pair of rearwardly sloping cutting faces which merge to form a radial cutting edge whose outer end is the outermost tip of the respective Wing, the outer surface of each wing between the outer ends of the respective pair of cutting faces comprising a respective pair of merging salient faces, the line of juncture between the salient faces defining a scouring edge, said edge sloping rearwardly and inwardly toward the longitudinal axis ofthe bit and lying radially outward of any circle which can be drawn through all of the said outer ends of the cutting faces.

MALCOLM H. HUBBACK.

REFERENCESV CITED The following references are of record in the filerof this patent:

UNITED STATES PATENTS Number Name Date 1,671,458 Wilson May 29, 1928 1,929,608 Rea Oct. 10, 1933 2,006,536 Brown July 2, 1935 2,051,525 Howard Aug. 18, 1936 2,297,983 Rea Oct. 6, 1942 2,401,834 Liddicoat June 11, 1946 FOREIGN PATENTS Number Country Date 112,585 Australia Feb. 20, 1941 

